If you want to read them in order than the [url=http://halo.wikia.com/wiki/Kilo-Five_trilogy]kilo-5 trilogy[/url] which consists of Grasslands, The Thursday War and Mortal Dictata. The first book, grasslands includes what happens after Onyx though the three books mostly follows a different group of characters (trying not to spoil anything so forgive me if what i'm saying doesnt make sense). I could summarize the trilogy if you like just pm me so nothing gets spoiled for anyone else. There is also another once coming out on the 16th called [url=http://halo.wikia.com/wiki/Halo:_Hunters_in_the_Dark]Hunters in the dark[/url] which follows a joint team of Spartans and elites as they return to the ark. There are also two books that have already been released. [url=http://halo.wikia.com/wiki/Halo:_Broken_Circle]broken circle[/url] is about the great covenant schism that happened in H2 and touches on the Elite and Prophet relationship. I thought it was a pretty good read if your interested in Covenant history. The last one is an electronic book called [url=http://halo.wikia.com/wiki/Halo:_New_Blood]new blood[/url]. if you liked Halo ODST then you'll love this book. If you wanted to learn what happened to the ODST squad than you should read this. It's a short book so itll be quick, the ending has a lot of people guessing what is going to happen in H5 hope this helps!

How good are the Halo books?

Grasslands takes place on Onyx, but it sucks. Try the Forerunner Trilogy